King County · System ID 51400 · Community water system
Is Maplewood Addition Water Coop’s water safe? PFAS test results (King County, WA)
PFAS detected — below state action levels
Maplewood Addition Water Coop detected PFAS in 1 of its 1 tested water source; every result in the current state dataset (2021–present) is below Washington’s state action levels (latest test June 2026).
Community water system serving King County · 155 connections · about 435 people.
At least one individual sample measured at or above a federal MCL value (4 ng/L for PFOA/PFOS; 10 ng/L for PFHxS, PFNA, HFPO-DA). Compliance with the federal standard is judged on running annual averages at the tap — a single source sample at that level is a flag, not a violation.
PFAS results on record for Maplewood Addition Water Coop
| Analyte | Highest result | WA action level | Federal MCL | Detected at source |
|---|---|---|---|---|
| PFOS Perfluorooctanesulfonic acid | 4 ng/L | 15 ng/L | 4 ng/L | Wells 1,2&3 |
What this means
PFAS was detected in 1 of the 1 sources tested for this system, and every result in the current state dataset (2021–present) is below Washington’s state action levels — the thresholds at which the state requires customer notification and action. Detected-but-below-action-level is exactly what it sounds like: PFAS is present in at least one source at low levels, and the state does not currently require the utility to act on it.
If you’d rather not drink detectable PFAS at any level, the at-the-tap option we plan to offer is under-sink reverse osmosis — manufacturer test data shows RO membranes reduce PFAS. See the planned systems.
These results describe the water system’s sources (wells, intakes), not any individual tap — utilities blend, treat, and rotate sources. Data: Washington State Department of Health public PFAS results and Drinking Water Service Areas, dataset updated 2026-07-22. Latest test on record for this system: 2026-06-22. Informational only — not a certification of water quality and not health advice. If you have concerns about your drinking water, contact your utility or the WA DOH Office of Drinking Water.
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